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PubMed1979

The effect of delayed feedback on infant learning reexamined.

The study reexamines the effect of delayed reinforcement upon contingency behavior in 6- to 8-month-old infants and attempts to account for the temporal discrepancy between span of integration and contingency memory. A modified delayed-reinforcement scheduling procedure enabled a previous methodological criticism to be discounted. The findings confirmed that whereas infants revealed reliable acquisition under immediate reinforcement, a 3-sec delay (whether reset or nonreset) precluded response acquisition, as did 6-sec and 10-sec delay of reinforcement. The findings are interpreted in terms of an informational-load hypothesis which relates short-term memory to the integration and/or segregation of multimodal input.

Conditioning, Operant↗
PubMed1982

Effects of septal lesion on go, no-go differentiation and reversal learning in rats.

Experiments were done on 24 Sprague-Dawley male albino rats. Acquisition of go, no-go differentiation and its reversal were compared between normal and septal animals. Rats were trained in Skinner boxes on a 30-s VI food reinforcement schedule. Differentiation sessions consisted of periods with flashing and steady light on, randomly distributed. In half the subjects of each group reinforcement was available only during the flashing light (CS+ periods) while during the steady light no reinforcement was delivered (CS- periods). For the remaining subjects the allocation of stimuli as CS+ or CS- was reversed. During reversal training the signalling properties of the stimuli were reversed. The experiments confirmed that there is lesion-induced increment in base-line response rate. During differentiation training septal damage had no significant effect on the proportion of total responses emitted during CS-, although it increased the overall rate of CS- responding when the flashing light was used as CS-. During reversal training when the flashing light was used as CS- septal animals both responded at a higher rate during CS-, and emitted a higher proportion of their responses during CS-, relative to controls. There were no lesion effects on CS- responding when the steady light was used as CS-. Thus the septal deficit appeared when the to-be-extinguished habit was fairly strong and only under conditions of greater stimulus generalization. These results indicate that septal effects depend on a variety of experimental factors determining performance in any given test situation, among which stimulus intensity dynamism is one of particular importance.

Analysis of Variance↗
PubMed1966

The motivational properties of schedule-induced polydipsia.

Schedule-induced polydipsia occurred during initial magazine training to Noyes pellets (45 mg), disappeared when lever-pressing was acquired on a continuous reinforcement schedule (CRF), and reappeared when the food contingency was changed to a 1-min variable interval schedule (VI 1 min). Polydipsia also developed under a VI 1 min food schedule when water was concurrently available on various fixed ratios (FR), rather than being freely available. The level of the polydipsia and its motivating properties allow it to be classified as a form of adjunctive behavior.

Animals↗
PubMed1978

Cocaine reinforced progressive ratio performance in the rhesus monkey.

A series of experiments were conducted to determine the effectiveness of a progressive ratio (PR) procedure in measuring the relative reinforcing efficacy of several intravenous doses of cocaine. In Experiment 1, utilizing much smaller increases in the ratio requirement than previously reported, the animals generally displayed increases in breaking point with increases in the cocaine unit dose up to 0.4 mg/kg/inj. The highest dose studied (0.8 mg/kg/inj.) engendered breaking points lower than the 0.4 mg/kg dose but higher than the remaining lower doses. Experiment 2 was conducted utilizing the same reinforcement schedule as in Experiment 1 but with liquid Tang as the reward. The results demonstrated that this procedure would function to discriminate reinforcing strength with a more traditional reward. Experiment 3 examined a more expedient procedure to see if results similar to those seen in Experiment 1 could be obtained in a shorter period of time. However, the shorter procedure engendered excessive intrasubject variability, suggesting that some intermediate level of baseline experience between the 5-7 days used in Experiment 1 and the 50 reinforced responses used in Experiment 3 would be necessary to obtain consistent breaking point-unit dose functions.

Animals↗
PubMed1969

Variability of response location for pigeons responding under continuous reinforcement, intermittent reinforcement, and extinction.

The effect of several reinforcement schedules on the variability in topography of a pigeon's key-peck response was determined. The measure of topography was the location of a key peck within a 10-in. wide by 0.75-in. high response key. Food reinforcement was presented from a magazine located below the center of the response key. Variability in response locus decreased to a low value during training in which each response produced reinforcement. Variability increased when fixed intervals, variable intervals, random intervals, or extinction were scheduled.

Journal Article↗
PubMed1978

Effect of variable-interval punishment on the behavior of humans in variable-interval schedules of monetary reinforcement.

One male and three female human subjects pressed a button for monetary reinforcement under a range of variable-interval schedules specifying different frequencies of reinforcement. On alternate days, responding was also punished (by subtraction of money) according to a variable-interval 170-second schedule. In the absence of punishment, the rate of responding was an increasing negatively accelerated function of reinforcement frequency, as predicted by Herrnstein's equation. The effect of the punishment schedule was to suppress responding under lower frequencies of reinforcement; responding under higher reinforcement frequencies was much less affected. This was reflected in an increase in the value of K(H) (the constant expressing the reinforcement frequency corresponding to the half-maximal response rate), whereas there was no significant change in the value of R(max) (the constant expressing the maximum response rate). Previous results had shown that variable-ratio punishment resulted in a change in the values of both constants (Bradshaw, Szabadi, and Bevan, 1977). The results of the present study were consistent with the concept that the suppressive effects of punishment on responding depend on the nature of the punishment schedule.

Journal Article↗
PubMed1972

Two different kinds of key peck in the pigeon: some properties of responses maintained by negative and positive response-reinforcer contingencies.

Pigeons emitted almost exclusively short-duration key pecks (shorter than 20 msec) when on negative automaintenance procedures, in which pecks prevented reinforcement. Peck durations under fixed-interval and fixed-ratio reinforcement schedules were generally two to five times longer than pecks under a negative automaintenance schedule. However, initial key pecks were of short duration, independent of procedure. The frequency of short-duration pecks was insensitive to differential reinforcement, while the frequency of long-duration pecks was sensitive to differential reinforcement. It is proposed that short-duration pecks arise from the pigeon's normal feeding pattern and are directly enhanced by food presentation, while long-duration pecks are controlled by the contingent effects of food presentation. The implications of the existence of two classes of pecks for the functional definition of operants and the separation of phylogenetic and ontogenetic sources of control of key pecking are discussed.

Journal Article↗
PubMed1990

Behavioural analysis of the anorectic effects of fluoxetine and fenfluramine.

Two sets of experiments were carried out to compare the effects of fenfluramine and fluoxetine on consummatory and operant behaviour. In food-deprived rats allowed access to a 35% sucrose solution, an initial period of sucrose consumption was followed by a short period of grooming and exploratory behaviour, later superceded by resting. This "behavioural satiety sequence" was advanced by fluoxetine, but disrupted by dl-fenfluramine, which suppressed post-prandial resting, even at sub-anorectic doses. Fluoxetine also elicited resting behaviour following water drinking. However, this did not appear to be a non-specific sedative effect, since fluoxetine increased post-prandial grooming. In rats performing on random interval schedules of food reinforcement, fluoxetine caused proportionally greater decreases in responding on a reinforcement-lean schedule (RI-300s), as compared to a reinforcement-rich schedule (RI-7.5s); this effect is similar to that of a reduction in level of food deprivation. By contrast, fenfluramine reduced responding equally on both schedules. In both paradigms, the effects of fluoxetine were compatible with an increase in postprandial satiety, but the effects of fenfluramine were not.

Animals↗
PubMed1998

Matching under nonindependent variable-ratio schedules of drug reinforcement.

Response-contingent deliveries of oral pentobarbital maintained responding of 3 rhesus monkeys during daily 3-hr sessions. Deliveries of pentobarbital were arranged under nonindependent concurrent variable-ratio variable-ratio schedules. Responses to either schedule counted toward completion of both variable-ratio schedule requirements. This schedule is similar in some respects to conventional concurrent variable-interval variable-interval schedules, in which passage of time counts toward completion of the interval value on both schedules. Restricted nonindependent concurrent variable-ratio variable-ratio schedules were also studied. On that schedule, when a drug delivery was assigned to one spout, it had to be collected before responses on the opposite spout again counted toward completion of the schedule requirements. Relative reinforcer magnitude was varied by changing the drug concentration on one schedule while keeping the drug concentration constant on the other variable-ratio schedule. Under both types of concurrent variable-ratio schedules, the relative rate of responding corresponded to the relative drug intake. Unlike earlier studies of concurrent variable-interval variable-interval intravenous cocaine reinforcement, preference was proportionate to concentration, and exclusive preferences did not develop. The relationship between relative rate of responding and relative drug intake was well described by the generalized matching law.

Animals↗
PubMed1999

Concurrent progressive-ratio schedules to compare reinforcing effectiveness of different phencyclidine (PCP) concentrations in rhesus monkeys.

RATIONALE: Progressive ratio (PR) schedules have become well accepted for testing the reinforcing effectiveness of drugs. This study extends the methods to concurrent PR schedules with different concentrations of orally delivered phencyclidine (PCP). OBJECTIVE: The sensitivity of the procedure is tested by presenting different PCP concentrations with independently-operating PR schedules. METHOD: PCP self-administration was investigated in seven rhesus monkeys. Six different PCP concentrations (0.03-1.0 mg/ml) and water were randomly paired (21 pairings). Liquid delivery (24 ml) was contingent upon lip-contact responses on solenoid-operated drinking spouts; whereby, the response requirement or fixed-ratio (FR) increased (from 8 to 16, 32, 64, 128... to 4096) after each successful completion of a previous FR and subsequent liquid delivery. Monkeys self administered PCP during daily 3-h sessions, and each pair of concentrations was held constant until behavior had stabilized for at least 4 days. RESULTS: The higher of the two PCP concentrations always maintained greater responding, PR break point (BP), or the last ratio completed, and liquid deliveries than did the lower concentration. However, the monkeys did not exclusively respond on the drinking spout that yielded the higher drug concentration. When examined across all drug pairings, the percentage of total available deliveries of the higher concentration was significantly greater than those of the lower concentration. The monkeys maximized the amount (mg) consumed for the response output. Responding, BPs and liquid deliveries maintained by 0.12 and 0.25 mg/ml PCP were significantly greater than other PCP concentrations; however, drug intake (mg) increased directly with PCP concentration. CONCLUSION: These results indicate that concurrent PR schedules using oral drug self-administration and a concurrent choice paradigm reliably provide an estimation of relative reinforcing strength, and behavior maintained by these schedules is sensitive to small changes in PCP concentration.

Administration, Oral↗
PubMed2003

Effects of free-food deliveries and delays on choice under concurrent-chains schedules.

Pigeons responded on a concurrent-chains schedule with two equal variable-interval (VI) schedules as initial links and delays to food of 3 and 12s as the two terminal links. In even-numbered sessions, no other reinforcement schedule was present, and all pigeons showed a strong preference for the response key that had the shorter, 3-s terminal-link delay. In odd-numbered sessions, the initial links were interrupted at random times by one of three different types of events. When the interruptions were immediate food deliveries, the response percentages increased on the key that had the 3-s delay. When the interruptions were 30-s delays followed by food, the response percentages remained approximately unchanged. When the interruptions were 30-s delays with no food, the response percentages decreased. The results were used to compare the predictions of different mathematical models of concurrent-chains performance. The results favored models that assume that preference is determined by the relative amount of advantage that is gained when a terminal link is entered.

Journal Article↗
PubMed1971

Behavioral contrast as a function of the duration of an immediately preceding period of extinction.

For four pigeons key-peck responding was reinforced on a variable-interval reinforcement schedule in the presence of a vertical white line. When response rates had stabilized a horizontal white line was introduced, in the presence of which reinforcement was not available (extinction). The horizontal line was presented once per session, immediately before the vertical line was presented. The duration of the horizontal line varied randomly from session to session, being either 0 sec (i.e., no presentation), 10 sec, 30 sec, 2 min, 10 min, 40 min, or 120 min. When the horizontal line was present for more than 0 sec, behavioral contrast was obtained in the presence of the following vertical line. Contrast increased with increasing durations of the horizontal line, asymptoting when the horizontal line was present for 40 min.

Journal Article↗
PubMed1972

Variable location of punishment in a response sequence.

Key pecking of pigeons under a fixed-ratio 100, grain reinforcer schedule was followed by electric shock occurring once in each sequence of 100 responses with the shocked response varying irregularly in successive sequences. Under this shock schedule, a localized suppression of responding in a response sequence was not correlated with the probability of shock at different points in the sequence. High shock levels increased the duration of post-reinforcement pauses and suppressed responding during the first half of the response sequence. This suppression often persisted after the shocked response when shock occurred early in the sequence. The shock schedule did not produce a consistent suppressing effect on responding during the last half of the response sequence.

Journal Article↗
PubMed1994

Tobacco abstinence, smoking cues, and the reinforcing value of smoking.

One definition of the reinforcing value of a drug is the degree to which an organism will work to obtain it. Male and female smokers (n = 8 each) engaged in a task involving concurrent schedules of reinforcement for responding to receive cigarette puffs versus money on four occasions, following overnight abstinence versus no abstinence and in the presence of a lit cigarette (smoking "cue") or with no cigarette (2 x 2 design). Reinforcement schedule for puffs ranged from variable ratio 4 (VR4) to VR32, with schedule order during the first five trials (VR4 first, VR32 first) counterbalanced and repeated in reverse sequence during the second five trials. Schedule for money remained at VR4 during all trials. Results indicated significantly greater responding for puffs after overnight abstinence and in the presence of the smoking cue, although effect of the cue was specific to the "leaner" VR schedules (VR16, VR32). Unexpectedly, not only was reinforcement schedule for puffs a significant determinant of responding, but the order of these schedules (i.e., VR4 first vs. VR32 first) produced a significant overall difference in responding for puffs, especially in the presence of the cue. There was no difference in responding between males and females. These findings indicate that the reinforcing value of smoking is increased by overnight abstinence, the presence of a lit cigarette under lean reinforcement conditions, and the order in which reinforcement schedules are presented.

Adult↗
PubMed1975

Maintenance of behavior controlling the duration of discriminative stimuli.

THE MAINTENANCE OF A RESPONSE CONTROLLING THE DURATION OF POSITIVE AND NEGATIVE DISCRIMINATIVE STIMULI IN A MULTIPLE SCHEDULE WAS EXAMINED WITH RESPECT TO THE POSSIBLE CONSEQUENCES OF THE RESPONSE: none, escape from the negative stimulus, production of the positive stimulus, and initiation of the reinforcement schedule associated with the latter. The last two seemed to be the major factors in producing and maintaining the response. Escape from the negative stimulus maintained it in most subjects, but only at a much lower level.

Journal Article↗